This invention relates to bouyant, towed electrodes of the cable type such as are used for sweeping of magnetic influence mines, and more particularly to a novel wire guide device and method for preconditioning such electrodes.
U.S. Pat. No. 3,940,732, issued to J. A. Hudson and M. J. Yelverton and assigned to the assignee hereof, describes a bouyant electrode of a cable type that is towed-along its axial length, by a helicopter for example, at substantial speeds through sea water. The electrode is energized to produce electrical currents in the sea water. Magnetic disturbances resulting from the electrical currents and the forward motion of the electrode are effective in sweeping magnetic influence mines. The electrode of that patent comprises a core or central strength member in the form of a synthetic filament rope, a cylindrical bouyant sleeve of a closed cell plastic foam material and an outer conductive layer formed of helically wound strands of aluminum wire. The aluminum wire strands are tightly bound with an aluminum wire serving in the forward portion of the electrode, and the forward end of the electrode is provided with a conductive metal lug or connector that is swaged or otherwise fixed to the strength member and provides for electrical connection to the serving and to the helical wires of the electrode. At the aft end of the electrode, the helical wires are bound to the bouyant sleeve by one or more metal bands, preferably of the screw tightened variety.
While the aforedescribed prior art electrode has many advantages, it has been found that it suffers one disadvantage in that excess aluminum wire is unavoidably distributed along the length of the electrode during the helical winding thereof and, during use, the excess tends to work its way along the electrode and accumulates at the aft end. The accumulation presents itself as a balooning out or enlargement in the wire layer resembling a bird nest just ahead of the band clamping the wire ends. In view of this, it has been the practice to precondition each electrode by towing it for a period of time until the bird's nest is formed, then removing the band clamp, manually cutting off the excess wire of each strand, re-shaping the end portions of the wire to the bouyant sleeve, and reclamping. Even with such preconditioning, there remains a tendency for the problem to repeat itself, possibly because as the bird's nest grows it becomes self-limiting in the amount of slack that can be pulled out of the helical wire winding by the hydrodynamic forces acting on the wire and the bird's nest.
U.S. patent application Ser. No. 828,714 filed Aug. 29, 1977, now U.S. Pat No. 4,117,447, and assigned to the assignee hereof, describes an electrode cable having an anti-birdnesting device in the form of a slide element that is key for axial movement along the aft end of the bouyant sleeve, and to which the wire ends are clamped. That device is intended to allow slack in the winding to work its way aft of the cable without generating a birds nest, and represents one useful approach to the problem of excess wire in the cable windings. It is, however, subject to disadvantages of requiring moving parts that are subject to possible binding and breakage under severe conditions of use.